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added FIR LPF, HPF and BPF

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Ahmet Inan 2019-01-03 21:13:56 +01:00
commit 00501fa433
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/*
Some finite impulse response filter functions
Copyright 2018 Ahmet Inan <inan@aicodix.de>
*/
#ifndef FILTER_HH
#define FILTER_HH
#include "const.hh"
#include "utils.hh"
#include "coeffs.hh"
namespace DSP {
template <typename TYPE>
class LowPass : public CoeffsFunc<TYPE>
{
TYPE f;
public:
LowPass(TYPE cutoff) : f(TYPE(2) * cutoff) {}
TYPE operator () (int n, int N)
{
TYPE x = TYPE(n) - TYPE(0.5) * TYPE(N - 1);
return f * sinc(f * x);
}
};
template <typename TYPE>
class HighPass : public CoeffsFunc<TYPE>
{
TYPE f;
public:
HighPass(TYPE cutoff) : f(TYPE(2) * cutoff) {}
TYPE operator () (int n, int N)
{
TYPE x = TYPE(n) - TYPE(0.5) * TYPE(N - 1);
// if (N%1) return delta(x) - f * sinc(f * x);
return sinc(x) - f * sinc(f * x);
}
};
template <typename TYPE>
class BandPass : public CoeffsFunc<TYPE>
{
TYPE f0, f1;
public:
BandPass(TYPE cutoff0, TYPE cutoff1) :
f0(TYPE(2) * cutoff0), f1(TYPE(2) * cutoff1) {}
TYPE operator () (int n, int N)
{
TYPE x = TYPE(n) - TYPE(0.5) * TYPE(N - 1);
return f1 * sinc(f1 * x) - f0 * sinc(f0 * x);
}
};
}
#endif